An object that provides thumbnail or preview images of assets independently of playback.
- iOS 4.0+
- macOS 10.7+
- tvOS 9.0+
AVAsset uses the default enabled video track(s) to generate images. Generating a single image in isolation can require the decoding of a large number of video frames with complex interdependencies. If you require a series of images, you can achieve far greater efficiency using the asynchronous method,
generate, which employs decoding efficiencies similar to those used during playback.
You create an asset generator using
asset. These methods may succeed even if the asset possesses no visual tracks at the time of initialization. You can test whether an asset has any tracks with the visual characteristic using the
AVAsset class’s method
Assets that represent mutable compositions or mutable movies may gain visual tracks after initialization of an associated image generator.